In general chemical processes, heat exchange is made at various routes by way of reactors and distillation columns, and waste heat generated after such heat exchange can be re-used or discarded. For example, as in FIG. 1, when the waste heat is a low-grade heat source having a level of less than 120° C., for example, 70° C. to 110° C., it has a low temperature such that it is impossible to be essentially re-used, and thus the waste heat is discarded after condensing the condensate water.
Furthermore, low-pressure or high-pressure steams are used in various applications in the industrial fields and particularly, in the chemical processes, high temperature and pressure steams are mainly used. The high temperature and pressure steams are generally produced by heating normal temperature and pressure water to the vaporization point and applying high pressure to water turned into vapor to increase internal energy, where it is required to consume a large amount of energy in order to vaporize liquid water.
In order to solve the above problem, a heat recovery apparatus for recovering the low-grade heat source using a heat pump system is disclosed in Patent Document 1. However, in the case of the heat recovery apparatus, since only one of the refrigerant streams was heat exchanged with the waste heat stream to recover energy, there was a problem to require much energy, in order to compress the low temperature and pressure refrigerant stream flowing into the compressor into high temperature and pressure refrigerant stream.
(Patent Document 1) KR 2015-0000422A